The present invention relates to a golf club head made of a combination of two or more different metallic materials.
To meet the requirements for increased flying distance of a ball hit with a golf club, feeling of ball hitting with the club, etc., various proposals have heretofore been made as to golf club heads made of two or more different metallic materials in combination, so-called hybrid metallic golf club heads. A typical one of such well-known metallic golf club heads is illustrated in FIG. 1. A golf club head shown in FIG. 1 is that of a so-called "wood" club. A face portion 100 of this club head is made of a titanium alloy while the rest 101 thereof is made of stainless steel. FIG. 2 shows the head of a so-called "iron" club. A face portion 200 of this iron club head is made of a titanium alloy while the rest 201 thereof is made of beryllium copper or stainless steel. Further, some wood club heads are also known of which a sole portion is made of kind of metal while the rest thereof is made of another kind. In such conventional golf club heads, the metallic materials of different kinds are joined to each other by screwing the face portion 100 (200) of the club head to the rest 101 (201) thereof, force fitting the face portion to the rest or bonding the face portion to the rest with an adhesive.
However, such conventional joining methods result in a shift of one joint boundary with respect to another, insufficient joining strength and thus poor durability. Further, taking the strength and durability of the golf club head into consideration leads to a limitation of the joining area. Thus, even if an optimum combination of different metallic materials is designed for a lower and deeper center of gravity, increased moment of inertia and improved feeling of ball hitting, the limitation of the joining area makes it difficult to manufacture a golf head exactly as designed.